How to mount Sram GXP® and BB30 Oval BOOST148 chainring:

You need to unscrew these 3 torx t-25 bolts from the crank. Then remove the spider+chainring combo you currently have there. Clean the splines and put some grease on them. Position the chainring in place (note there is only one way to fit this Sram chainring so you don't have to worry how to do it). Close all 3 bolts to about 5-7Nm.